MC sleeps and whenever she sleeps, she teleports into another universe. She only comes back when she goes to sleep again. If she sleeps on 10 PM, she will be on the other universe as soon as she sleeps (like 11 PM) and she will continue from that time.

I like this idea! Kind of like Sucker Punch? Maybe something bad from the other universe wants to break through into the real world, maybe MC gets clues from her dreams on how to stop it - and in the end MC has to choose whether to stay in the alternative universe or in the real world?